The present invention relates to complex high frequency components used in wireless circuits such as cellular phone terminals and also to communication devices using these components.
Cellular phone terminals have been rapidly being downsized with their increased performance. In order to achieve their downsizing, each high frequency component used in a wireless circuit has been being miniaturized.
Conventional high frequency components used in a wireless circuit include a balanced to unbalanced transducer (hereinafter referred to as the balun). The balun is a device with the function of converting unbalanced line signals into balanced line signals, and vice versa. An example of a structure of the balun will be described as follows. FIG. 13 shows a chip trans as an example of the balun.
The chip trans has a multilayer structure of dielectric substrates 54a-34e. The dielectric substrates 54a, 54e have shield electrode layers 56, 70, respectively, on one of their main surfaces. The dielectric substrate 54b has a connection electrode layer 60 on one of its main surfaces. The dielectric substrate 54c has a first strip line 62 on one of its main surfaces. The first strip line 62 is composed of first and second parts 64a, 64b which are coiled. The dielectric substrate 54d has second and third coiled strip lines 66, 68 which are coiled on one of its main surfaces. The second and third strip lines 66, 68 are electromagnetically coupled with the parts 64a, 64b, respectively, of the first strip line 62.
As described above, conventional baluns composed of a chip trans as shown in FIG. 13 have been being downsized. In addition, it has been being developed to downsize a filter with the function of selectively passing or attenuating the predetermined frequencies with respect to the high frequency signals to be supplied to or outputted to the balun.
However, the conventional balun and filter are mounted on different circuit substrates with each other, and this arrangement increases the number of components, thereby impeding cost reduction. This arrangement also makes it difficult not only to miniaturize a wireless circuit into which the balun and the filter are integrated but also to miniaturize a communication device like a cellular phone terminal into which the wireless circuit is integrated.
In view of the above situation, the present invention has an object of downsizing the high frequency component into which a balun and a filter are integrated, and thereby downsizing the communication device like a cellular phone terminal into which the high frequency component is integrated.
The other objects, features, and advantages of the present invention will be clarified below.
The present invention can be summarized as follows.
In order to solve the above-described problems, the complex high frequency components of the present invention each include a balun which mutually converts balanced line signals and unbalanced line signals, and a filter which is electrically connected to the balun and passes or attenuates the predetermined frequency bands. Such complex high frequency components of the present invention comprise an electrode layer and a dielectric layer which compose the electric patterns for the balun and the filter, and are integrally stacked.
Using these complex high frequency components can provide a communication device with a reduced size and excellent properties.